1. Evidence for Evolution
Day 1

2. Evidence for the Theory of Evolution
How do we know this is not what the Earth looked like when the dinosaurs existed?

3. Benchmarks
SC.912.L.15.1 Explain how the scientific theory of evolution is supported by the fossil record, comparative anatomy, comparative embryology, biogeography, molecular biology, and observed evolutionary change.
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The primary benchmark for today’s lesson is SC.912.L However, please be aware that this benchmark also asses most of the Nature of Science strands.

4. Objective
Explain how evidences such as fossils, biochemical similarities, embryonic development, homologous and vestigial structures, and similarities and differences between organisms in different parts of the world are used to substantiate biological changes through time.

5. Essential Questions
How is Darwin’s idea of “Descent with Modification supported by the different types of evidence for evolution?
If the DNA of a whale, a hippopotamus, and a camel were analyzed, what kind of findings would you expect to see?

6. Evidence for Evolution
Remember…
In his book, Darwin presented evidence that evolution has been taking place for millions of years—and continues in all living things.
But exactly what evidence of evolution did Darwin present?

7. Evidence for Evolution
Darwin argued that living things have been evolving on Earth for millions of years, and that evidence for this process could be found in:
The fossil record.
The geographical distribution of living species.
The comparative anatomy of living organisms.
The similarities in early development, or embryology.
The similarities in molecular biology, or DNA analysis.
This presentation will provide a quick review of all of these types of evidence. However, the focus of today’s activities will be on molecular evidence for evolution. Students should receive detailed instruction on the others in their regular Biology class.

8. The Fossil Record
Darwin saw fossils as a record of the history of life on Earth.
By comparing fossils from older rock layers with fossils from younger layers, scientists could document that life on Earth has changed over time.

9. Geographic Distribution
On the Galapagos Islands, Darwin observed that each island had a species of finch that was distinctly different from those on the other islands, and on the mainland of South America.
Darwin concluded that this was evidence that over time, organisms could descended with modification from a common ancestor, as populations adapted to different environments.

10. Geographic Distribution
Based on his observations of similar yet unrelated organisms living on different continents, Darwin also concluded that organisms that descended from different ancestors could evolve similar anatomies and behaviors if they lived under similar conditions and were exposed to similar pressures of natural selection.
The Coypu and the Muskrat in the figure appear to be quite similar. While they are both rodents, they are not closely related species. Their similarities are due to convergent evolution, in which two distinct species of differing lineages evolve similar characteristics as a result of being exposed to similar selection pressures in the environments they inhabit. The same is true of the Capybara and the Beaver.

11. Comparative Anatomy
Similarities in bone structures also provide strong evidence for evolution.
Anatomical features that are similar in structure are called homologous structures, and they indicate common ancestry.
Be sure to emphasize that homologous structures ate similar in structure but are not necessarily similar in function. Ask the students to compare the limb structures in the figure and infer evolutionary relationships based on their observations. Which of these organisms do you think might be our closest relative? Which appears to be our most distant relative?

12. Comparative Anatomy
Similarities and differences in homologous structures help biologists group animals according to how recently they last shared a common ancestor.
However, not all homologous structures serve important functions.
Some organisms have structures that are so reduced in size that they seem to serve no function, but they resemble functional structures in related organisms. These are called vestigial structures.
Whales have vestigial pelvic and femur bones within their bodies. What does the presence of these bones indicate about the whales’ evolutionary descent?

13. Embryology
The early stages, or embryos, of many animals with backbones are very similar.
The same groups of embryonic cells develop in the same order and in similar patterns to produce the tissues and organs of all vertebrates. This also indicates evolutionary relationships.

14. Molecular Biology Remember…
All cells rely on DNA to make proteins, by linking amino acids into a chain.
Using new technologies, biologists are able to determine the amino acid sequences in proteins.
The fact that this process of making proteins is common to all living things suggests that it has been passed down from an ancient ancestor.
Ask students to share their interpretations of the data table.
Comparing those amino acid sequences allows scientists to deduce evolutionary relationships between various species of organisms.

15. Check for Understanding
Humans, rabbits, and zebras all have an appendix, an organ in their digestive system. Although it serves digestive and immune functions in herbivorous animals such as rabbits and zebras, it does not seems to serve much of a function in humans.
What type of evolutionary evidence is this?
How could this be evidence of evolution?
Comparative Anatomy (vestigial structure)
This could suggest an a highly herbivorous diet in our ancestral past.

16. Check for Understanding
Scientists discover the hardened tracks of an ancient organism in a layer of rock and sediment that is 1.4 million years old.
What type of evolutionary evidence is this?
Why is this considered evidence of evolution?
The Fossil Record
It document the existence of ancient life forms that no longer exists.

17. Check for Understanding
The human gene for human muscle protein is different from orangutan gene for muscle protein in 4 places and different from a chicken’s gene in 25 places.
What type of evolutionary evidence is this?
Why is this considered evidence of evolution?
Molecular Biology
We can assume that organisms with DNA sequences that are more similar are more closely related than organisms with sequences that are more different.

18. Evidence for Evolution
Day 2

19. Evolution of Populations
How many different species do you see here? Do you think these frogs would all be considered part of the same species? Why? Why not? What is a species anyway?

20. Benchmarks
SC.912.L Discuss mechanisms of evolutionary change other than natural selection such as genetic drift and gene flow.
SC.912.L Describe how mutation and genetic recombination increase genetic variation.

21. Objectives
Explain how mechanisms other than natural selection contribute to changes in a gene pool (genetic drift, barriers to gene flow leading to speciation).
Identify and explain factors that can increase genetic variation in populations (mutations, gene flow).

22. Essential Questions
How are genetic drift and reproductive isolation related to the formation of new species?
The species found on islands such as the Galapagos Islands and Madagascar are extremely unique and found nowhere else on earth. Why is that?

23. Variation and Gene Pools
Remember…
Inherited genetic variation within populations is one of Darwin’s basic tenets of natural selection.
A population is a group of individuals of the same species that interbreed.
A gene pool consists of all genes, including all the different alleles, that are present in a population.

24. Sources of Genetic Variation
Remember…
The two main sources of genetic variation are mutations and the genetic shuffling (also known as recombination) that results from sexual reproduction.
Review Meiosis and crossing over.
Have students observe the picture. None of the kittens will look exactly like their mother or exactly like their father or exactly like any of their siblings. Why not?

25. Sources of Genetic Variation
Mutations
A mutation is any change in a sequence of DNA.
Mutations occur because of mistakes in DNA replication or as a result of radiation or chemicals in the environment.
Gene Shuffling
Most heritable differences are due to gene shuffling.
Crossing-over increases the number of genotypes that can appear in offspring.
Emphasize that mutations do not always affect an organism’s phenotype, and that not all mutations are harmful. Some mutation can prove to be beneficial to an organisms fitness.

26. Natural Selection Remember…
Natural selection affects which individuals survive and reproduce and which do not.
If an individuals dies without reproducing, it does not contribute its alleles to the population’s gene pool, but if it produces many offspring, its alleles stay in the gene pool and may increase in frequency over time.
Essentially, Evolution is any change over time in the relative frequencies of alleles in a population.
Review natural selection.

27. Genetic Drift
Natural selection is not the only mechanism by which populations can evolve!
Sometime changes in the allele frequency within a population occur by chance. This is called genetic drift.
The genes of the next generation will be the genes of the “lucky” individuals, not necessarily the healthier or “better adapted” individuals. That, in a nutshell, is genetic drift.
Before
After

28. Genetic Drift For example:
In small populations, individuals that carry a particular allele may leave more descendants than other individuals do, just by chance.
Over time, a series of chance occurrences of this type can cause an allele to become common in a population.
Have students look at the image and compare the original population with each of the new founding populations. They should understand the the resulting populations look the way they do because of random chance,

29. Gene Flow
Populations can also evolve as a result of changes in gene flow.
Gene flow is the process of genes moving from one population to another.
Many factors can contribute to the movement of genes between populations
For example:
The immigration and emigration of organisms.
The dispersal of seeds or spores.

30. Speciation
Natural selection, genetic drift and barriers to gene flow can all lead to changes in the relative frequencies of alleles in a population, which can lead to speciation.
Speciation is the formation of new species.
A species is a group of organisms that breed with one another and produce fertile offspring.

31. Speciation
The gene pools of two populations must become separated in order for them to become two separate species.
As new species evolve, populations become reproductively isolated from each other.
When the members of two populations cannot interbreed and produce fertile offspring, reproductive isolation has occurred.
Do you think the variation of species Darwin observed on the 13 Galapagos Islands could have evolved as a result of reproductive isolation? Why? Why not?

32. Speciation
Reproductive isolation can develop in a variety of ways, including:
Behavioral Isolation
Habitat Isolation
Geographic Isolation
Temporal Isolation
Gametic Isolation
Mechanical Isolation
Reduced Hybrid Viability
Hybrid Sterility

33. Speciation Behavioral Isolation
Behavioral Isolation occurs when two species attract mates by using different mating signals or courtship rituals.
For example: A male frog of one population could have a mating call to which the females of another population do not respond.

34. Speciation Habitat Isolation
Habitat Isolation occurs when two species live in the same geographical area, but do not meet because they live in different specific habitats in that area.
For example: A forest ecosystem could be inhabited many beetle populations but each one might have a distinct niche on a specific type of plant.

35. Speciation Geographic Isolation
Geographic Isolation occurs when two species live in the different geographic areas, and never meet in the wild.
For example: Two owl populations may inhabit completely separate regions.

36. Speciation Temporal Isolation
Temporal Isolation occurs when two species breed at different times. They could be separated by as little as a few hours, by seasons, or even by years.
For example: Different plants populations may bloom at different times of year. If one is in bloom when the other is not, it would be impossible for one population to cross-pollinate the other.

37. Speciation Gametic Isolation
Gametic Isolation occurs when two species cannot breed because their gametes (eggs and sperm) cannot interact, even when they come into contact with each other.
For example: Several populations of fish may spawn a the same time but may have eggs and sperm that are incompatible.

38. Speciation Mechanical Isolation
Mechanical Isolation occurs when two species cannot breed because they are anatomically (structurally) incompatible.
For example: Two horse populations might incompatible due to difference in size or body structure, which would make it impossible for mating to occur.

39. Speciation Reduced Hybrid Viability
Reduced Hybrid Viability occurs when two species can breed, but the hybrid offspring produced do not live to reproductive age.
For example: Sometimes the seeds of hybridized plants fail to germinate, even under optimal conditions.

40. Speciation Hybrid Sterility
Hybrid Sterility occurs when two species can breed and the hybrid offspring survive, but these hybrids are sterile.
For example: Two populations of lizards may be able to breed and produce viable offspring, but the offspring are sterile or lay eggs that fail to hatch.

41. Evidence for Evolution
Day 3

42. Hominid Evolution

43. Benchmarks
SC.912.L Identify basic trends in hominid evolution from early ancestors six million years ago to modern humans, including brain size, jaw size, language, and manufacture of tools.

44. Objectives
Identify early human ancestors in terms of their scientific names, place of origin, and evolutionary trends.

45. Essential Questions
How do the defining characteristics of hominids differ among the variety of species within the group.
How did characteristics such as brain size, jaw size, language, and the use of tool of tools change over the 6 million year time period that hominids have existed?
How have the changes that occurred in hominids’ brain size, jaw size, language, and tools over time lead to a more successful organism?

46. Hominid Evolution
Between 6 and 7 million years ago, the hominoid line, or the great apes, gave rise to hominids. The hominid family includes modern humans.
As hominids evolved, they began to walk upright and developed thumbs adapted for grasping.
They also developed large brains.

47. Hominid Evolution

48. Hominid Evolution
The skull, neck, spinal column, hipbones, and leg bones of early hominid species changed shape in ways that enabled later hominid species to walk upright.
Evolution of this bipedal, or two-foot, locomotion freed both hands to use tools.
Hominids evolved an opposable thumb that enabled grasping objects and using tools.
Hominids displayed a remarkable increase in brain size, especially in an expanded cerebrum—the “thinking” area of the brain.

49. Hominid Evolution There are as many as 20 separate hominid species.
This diverse group of hominid fossils covers roughly 6 million years.
All are relatives of modern humans, but not all are human ancestors.
Questions remain about how fossil hominids are related to one another and to humans.

50. Hominid Evolution
Researchers once thought that human evolution took place in steps, in which hominid species became gradually more humanlike.
Today researchers believe Hominid evolution did not proceed by the simple, straight-line transformation of one species into another.
Rather, a series of complex adaptive radiations produced a large number of species whose relationships are difficult to determine.
Adaptive radiation is a process by which a several species evolve a single ancestral species.

51. Hominid Evolution
The hominid fossil record dates back 7 million years, close to the time that DNA studies suggest for the split between hominids and the ancestors of modern chimpanzees.
Millions of years ago

52. Hominid Evolution
Other species in the genus Homo existed before Homo sapiens.
The first fossils in the genus Homo are about 2.5 million years old.
These fossils were found with tools, so researchers called the species Homo habilis, which means “handy man.”

53. Hominid Evolution
2 million years ago, a species called Homo ergaster appeared. It had a bigger brain and downward-facing nostrils that resembled those of modern humans.
At some point, either H. ergaster or a related species named Homo erectus began migrating out of Africa through the Middle East.

54. Hominid Evolution
The story of modern humans over the past 500,000 years involves two main groups.
The earliest of these species is called Homo neanderthalensis.
Neanderthals lived in Europe and Asia 200,000–30,000 years ago.
They made stone tools and lived in organized social groups.
The other group is Homo sapiens—people whose skeletons look like those of modern humans.

55. Hominid Evolution
50,000–40,000 years ago some populations of H. sapiens seem to have changed their way of life:
They made more sophisticated stone blades and elaborately worked tools from bones and antlers.
They produced cave paintings.
They buried their dead with elaborate rituals.
About 40,000 years ago, a group known as Cro-Magnons appeared in Europe.
By 30,000 years ago, shortly after the appearance of Cro-Magnons, Neanderthals had disappeared from Europe and the Middle East.
For about 10,000 years, our species has been Earth’s only hominid.

56. Hominid Evolution
About 40,000 years ago, a group known as Cro-Magnons appeared in Europe.
By 30,000 years ago, shortly after the appearance of Cro-Magnons, Neanderthals had disappeared from Europe and the Middle East.
Cro-Magnons, the earliest members of our species, differed only slightly from modern humans. For about 10,000 years, our species has been Earth’s only hominid.